Residents are concerned about the long-term health effects of last week's coal ash spill, one of the worst in U.S. history. Relations with a Depression-era federal utility are damaged, too.

ROANE COUNTY, TENN. — The gunk on the water had thinned to a gray scrim in front of Mike Thomas' riverfront home -- a small sign of progress one week after one of the worst coal ash spills in American history.

But as Thomas drove along the bluff over the Emory River, he pointed to big piles of sludgy, dark gray ash, a byproduct of coal combustion, that had been accidentally disgorged by the nearby electricity plant. The heaps jutted from the water's surface like ugly volcanic islands. By the shore, many neighbors' docks sat in ruins, destroyed by mammoth waves when the ash was released.

This wasn't what Thomas had in mind when he bought his retirement home nine years ago.

"It's like something you'd see in Cleveland or damned Newark, New Jersey," said Thomas, a 62-year-old Georgia native. "Not east Tennessee."

This week, hundreds of workers continued a massive cleanup around the Kingston Fossil Plant, a Tennessee Valley Authority facility that has been a mundane and welcome fixture here for the last half a century, until -- late at night and three days before Christmas -- it became a force of ruination. Earthen walls surrounding one of the plant's retention areas failed, sending more than a billion gallons of the ash -- enough to fill 1,500 Olympic-sized swimming pools -- coursing into surrounding waterways and a handful of private properties.

No one was harmed, but residents are worried about the long-term health effects from the ash, which contains potentially harmful contaminants such as arsenic. They are also worried about the threats to their economy and culture, long defined by the picturesque waterways that snake through the lush Appalachian hill country.

"We're worried about the arsenic and whatever other contaminants are in the water, and we're worried about anything getting airborne," Thomas said. "On a lower level, we're worried about recreation -- hunting, boating, fishing.

"And property values," he added, gesturing to a home that serves as an appendage to an expansive deck overlooking the quiet river. "This is my legacy to my children."

State and federal officials Wednesday were awaiting results of soil testing. Preliminary air tests show no problems, although windy weather could change that. Meanwhile, some water samples taken close to the ash piles have found levels of arsenic and other pollutants that exceed drinking water standards. Officials are monitoring private wells, and say drinking water in municipal systems is safe -- for now.

Company officials have not determined the cause of the wall failure. Nor can they say how long the cleanup will take, or how much it will cost.

With so many unanswered questions, life in this county of 54,000 people has entered an unpleasant state of limbo. Health officials have advised residents to stay away from the ash, and to wash their hands thoroughly if they do get around it. The county school system altered its bus routes to keep a safe distance from the spill. Recreational boating has been suspended on the Emory River, parts of which have been rendered impassable.

Residents like Jeff Spurgeon who built waterfront dream homes now find themselves steps away from a man-made ecological nightmare.

"It's devastating, it really is," said Spurgeon, 43. The phone company worker and his wife saved for years to build the 4,400-square foot brick home along a cove that has become, literally, a giant ashtray.

The disaster carries a hint of irony for longtime residents: If there was a concern about ecological threats, it came from a few miles south, where the TVA operates a nuclear plant; or a few miles northeast around the Oak Ridge National Laboratories, where a cleanup of nuclear arms production sites has dragged on for years.

The spill also promises to test the store of goodwill built up over the decades by the TVA, the mammoth federally owned utility created during the Depression to provide energy, flood control and economic development to a large swath of the rural South.

TVA measures brought stability to the three rivers that meet here -- the Emory, the Clinch and the Tennessee -- which were subject to deadly flooding. A dam to the south broadened the rivers' contours, helping popularize the area as a fishing and boating spot. More recently, waterfront real estate attracted retirees from around the country. The local economic development agency distributes brochures of lake scenes, with a now unfortunate slogan: "Overflowing with possibilities."

The utility completed the coal-powered electricity plant near the confluence of the three rivers in the mid-1950s. It was welcomed as a major employer, and it earned a reputation for safety. But residents like Spurgeon watched with some trepidation as the pile of ash next to the plant grew year after year, finally towering higher than 50 feet.

"I kind of wondered, 'How high can it go?' " he said. "Accidents happen, but I think this could have been prevented."